1. Field of the Invention
This invention relates to deflavoring and concentrating the proteinaceous component of oleaginous seed materials by solvent extraction.
2. The Prior Art
By deflavoring is meant the removal of objectionable flavor notes which are characteristic of certain oleaginous seeds, especially the soybean, such that the product after deflavoring may be considered organoleptically bland. Oleaginous seeds encompass such seeds as cottonseed, soybean, rape seed, peanuts and copra. For example, with respect to soybeans, the known oleaginous seed protein materials which are typically encountered in industry and are benefited by the instant process invention are defatted flakes and meal. However, with this important qualification: Certain oleaginous seed protein materials have been so extensively denatured and macroscopically altered by severe heat treatments that solvent extraction means are virtually without effect. For example, certain commercially prepared soybean meal fractions have been so severely damaged during toasting that a seared or cauterized surface on the meal particles prevents solvent transfer to the interior. In such cases, re-comminution of the process fraction is necessary to expose less damaged surface to the solvent.
The term "concentrating" refers to the selective removal of non-proteinaceous components of such oleaginous seeds such that the protein level of the resulting product is increased. A variety of methods are known for obtaining such products.
Examples of such products are soy concentrates and soy isolates. Soybean concentrate is a term applied to soybean protein materials which have been substantially defatted and leached of a varying amount of carbohydrate to enhance the protein content. The term soybean isolate is used to denote soy protein which typically has been obtained by extraction of concentrate or defatted meal with acidic or alkaline aqueous solutions and precipitation of the solubilized protein at its isoelectric point.
The solvent extraction apparatus and manipulative steps employed in this invention encompass any of the conventional equipment and techniques of commercial solvent extraction, batch-wise or continuous.
A great deal of prior art has been developed relative to process means for deflavoring oleaginous seeds -- particularly the soybean because of its unpalatable flavor which has colorfully, but accurately, been described as bitter, green beany, throat-catching, paint-like, solvent-like, cardboardy, and like terms singlularly applied or as a collective nuance. But, to date, no commercially advantageous scheme has been devised to remove these objectional flavors from the protein component. This fact is succintly conveyed, on occasions of critical evaluation of these prior art schemes, by the old saw: `It still tastes like soybeans`.
A shortcoming of prior art deflavoring process schemes, and, some process schemes designed to enhance relative protein concentration, is that by consequence of the process (e.g., steam extractions, hot alcoholic extractions, and harsh caustic treatments) the resulting protein is substantially denatured; thus, substantially destroying the utility of the protein for subsequent use in products which require the native functionality of the protein to be preserved intact. Such properties destroyed or substantially diminished by denaturization include water solubility, foamability, colloid formation (aqueous dispersions and gels), and heat setting properties. Thus, generally the prior art processes fail to achieve a bland tasting protein material; and in processes which can provide significant deflavoring substantial denaturization occurs.
Representative prior art schemes are detailed in the following publications: 48 Cereal Chemist 640 (1971), Eldridge, et al.; U.S. Pat. Nos. 3,023,107, Feb. 27, 1962, to G. C. Mustakas; 2,635,094, Apr. 14, 1953, to P. H. Belter, et al.; 2,495,706, Jan. 31, 1950, to L. I. DeVoss; 3,365,440, Jan. 23, 1968, to S. J. Circle, et al.; 2,278,670, Apr. 7, 1942, to P. Rauer; 3,043,826, July 10, 1962, N. J. Beaber, et al.; 3,734,901 to Hayes, et al., May 22, 1973; Belgium Pat. No. 772,811, granted Sept. 20, 1971.
Accordingly, it is an object of the present invention to deflavor oleaginous seed protein material by solvent extraction to yield an organoleptically bland product.
A second object of this invention is to deflavor oleaginous seed protein material without substantial detriment to the functionality of the native protein. That is, a combined object of the present invention is to optimize deflavoring and minimize the denaturization which frequently accompanies prior art procedures.